QSC PLX Series

Fan Speed Troubleshooting
FAN STUCK HIGH:
Q88 or Q89 failed
R30 or Rl55, Thermal Sense NTC, shorted to heatsink
R266 or R271 missing.
FAN DOESN’T RUN
Check fan voltage, should be 1 IV when cold, 29V when hot.
Voltage OK -- replace fan.
No Voltage: check Q91, 89, 90, R264 and 265 missing. Confirm that +/-15V is reaching circuit.
22